1. Field of the Invention
This invention relates to inkjet printing systems and printing methods and to receivers for use therewith.
2. Description Relative to the Prior Art
Inkjet printing has become recognized as a prominent contender in the digitally controlled, electronic printing arena because, e.g., of its non-impact, low noise characteristics and system simplicity. For these reasons, inkjet printers have achieved commercial success for home and office use and other areas. Inkjet printing mechanisms can be categorized as either continuous (CIJ) or Drop-on-Demand (DOD). U.S. Pat. No. 3,946,398, which issued to Kyser et al. in 1970, discloses a DOD inkjet printer which applies a high voltage to a piezoelectric crystal, causing the crystal to bend, applying pressure on an ink reservoir and jetting drops on demand. Piezoelectric DOD printers have achieved commercial success at image resolutions greater than 720 dpi for home and office printers. Great Britain Patent No. 2,007, 162, which issued to Endo et al., in 1979, discloses an electrothermal drop-on-demand ink jet printer that applies a power pulse to a heater which is in thermal contact with water based ink in an ink channel. A small quantity of ink rapidly evaporates, forming a bubble, which causes a drop of ink to be ejected from small apertures along an edge of an ink channel. This technology is known as thermal ink jet or bubble jet. Thermal ink jet printing typically requires that the heater generates an energy impulse enough to heat the ink to a temperature near 400xc2x0 C. which causes a rapid formation of a bubble. U.S. Pat. No. 4,346,387, entitled METHOD AND APPARATUS FOR CONTROLLING THE ELECTRIC CHARGE ON DROPLETS AND INK JET RECORDER INCORPORATING THE SAME, issued in the name of Carl H. Hertz on Aug. 24, 1982, discloses a CIJ system. Such a system requires that the droplets produced be charged and then deflected into a gutter or onto the printing medium. U.S. Pat. No. 5,739,831, entitled ELECTRIC FIELD DRIVEN INK JET PRINTER HAVING A RESILIENT PLATE DEFORMED BY AN ELECTROSTATIC ATTRACTION FORCE BETWEEN SPACED APART ELECTRODES, issued to Haruo Nakamura on Apr. 14, 1998, discloses an electric field drive type printhead that applies an external laser light through a transparent glass substrate. The laser light strikes a photo conductive material causing it to become conductive thus completing the electrical path for the electrical field. Completion of the electrical path causes the electrical field to collapse around individual segments. These segments are in a deformed state due to their electromechanical response to the applied electric field. The individual segments in contact with a body of ink relax causing a volume of ink to issue from a nozzle plate. U.S. Pat. No. 5,880,759 entitled LIQUID INK PRINTING APPARATUS AND SYSTEM, issued in the name of Kia Silverbrook on Mar. 19, 1999; U.S. Pat. No. 6,079,821 entitled CONTINUOUS INK JET PRINTER WITH ASYMMETRIC HEATING DROP DEFLECTION issued in the names of James Chwalek, et al.; and EP1215047A2 published in the names of Anagnostopoulos et al., on the other hand, disclose liquid printing systems that afford improvements toward providing for extended length printheads better suited for page wide high-resolution inkjet printing that can be fabricated economically. As used herein, the term xe2x80x9cpage widexe2x80x9d refers to printheads of a minimum length of about 4xe2x80x3 (10.2 cm). High resolution implies nozzle density, for each ink color, of a minimum of around 150 nozzles per inch to a maximum of around 6000 nozzles per inch.
One of the most damaging image defects in inkjet printing is coalescence or puddling which is observed when wet ink drops touch one another on the receiver surface. This coalescence artifact, which often occurs in high-speed printing, causes images to appear blotchy or xe2x80x9cpuddledxe2x80x9d, resulting in non-uniformity in solid fill areas. As noted by Palmer et al. in the publication entitled, xe2x80x9cInk and Media Development for the HP PaintJet Printerxe2x80x9d, August 1988 U.S. Hewlett-Packard Journal pages 45-50, overhead transfer film may have an image recorded thereon wherein the drops are allowed to spread by a factor of 3.5xc3x97 until optimal overlap of adjacent dots is achieved. To avoid the touching of drops on the receiver surface, the maximum drop diameters shortly after the impact must be less than the pixel spacing. The dot size must then grow considerably after the drops have penetrated the surface to reach the optimum dot size. Furthermore, in Morris et al. U.S. Pat. No. 4,914,451 a method of printing is described in which ink dots are printed on a receiver medium so that the dots are a size of less than 1/R and the dots are allowed to grow to about 2.0/R. However, in the examples provided by Morris et al. post-printing image development must be provided in the form of terminating radial diffusion by solvent elimination particularly by placing the image medium between removable protective sheets. Furthermore, Morris et al. in all of their examples refer to two-pass printing and thus fail to recognize that high-speed single pass printing can be realized without coalescence of the drops.
Adamic and Gibney (European Pat. Appl. 0 544 487 A1) disclose the use of an additive (e.g., ployether polyol) in the ink to reduce the surface tension of the ink and increase the drop mass per firing. Reduced surface tension increases the wettability of ink on paper and thus enables faster ink penetration into the paper. This would alleviate the coalescence problem. However, decreasing the surface tension of ink would affect the jettability of the printhead, particularly for a piezo printhead. Furthermore, it would increase the dot size and thus reduce the print quality.
Lin et al. (U.S. Pat. No. 4,748,453) disclose a method of depositing spots of liquid ink upon selected pixel centers in a checkerboard pattern on overhead transparencies so as to prevent the flow of ink from one spot to an overlapping adjacent spot. This method uses at least two passes to complete the deposit of ink on all the pixels in a desired area. However, the use of N-pass printing, N greater than l or multipass printing, would reduce the printer productivity by a factor of N.
In this invention, we describe a high-speed single pass coalescence-free inkjet printing system and method by controlling both the spreading of drops on the receiver surface and the spreading of dots within the receiver. The control of drop and dot spreading are achieved by the proper selection of drop size and the selection of receiver medium characteristics.
As used herein the term xe2x80x9csingle pass printingxe2x80x9d refers to printing wherein ink drops are permitted to be deposited simultaneously or substantially simultaneously at adjacent pixel locations during relative movement between the printhead and the receiver medium. This is distinguished from non-single pass printing wherein predetermined patterns are established to insure that adjacent pixel locations do not have ink drops deposited simultaneously or substantially simultaneously to prevent coalescence of the drops. Thus in such non-single pass printing systems or modes a second, third or fourth pass is initiated to fill in ink drops at particular locations that were skipped during the first pass. It will be understood that the invention is directed to systems and methods that operate in a single pass printing mode and that such may be a mode of operation for high-speed operation of a particular printing apparatus which may also have the capability to operate in a multipass printing mode.
In accordance with a first aspect of the invention, there is provided An inkjet printer system for recording an image in a single pass print mode, the printer system comprising a printhead having a plurality of nozzles and selectively operable for depositing drops of liquid ink or other liquid used in forming of an image in a single pass print mode upon a surface of a receiver medium with a printing resolution R, a dot size Di of the dots resulting from impact of the drops with the receiver medium being in the range of 0.5/R less than Di less than 1/R and a final dot size D after spreading on the surface being in the range of 2xc2xd/R less than D less than 2.0/R; and the receiver medium having a surface for receiving the drops, a region of the medium proximate the surface having an influence upon drop spreading and the region having a porosity in the range of 0.2 to 0.8 and sufficient to provide a media drop spread factor Sm wherein Sm=D/Di with 2xc2xd less than Sm less than 2xc3x972xc2xd.
In accordance with a second aspect of the invention, there is provided a receiver medium or package thereof for use in an inkjet printer system wherein drops of liquid ink or other liquid used in forming of an image may be deposited upon the receiver medium in a single pass print mode with a printing resolution R, a dot size Di of the dots resulting from impact of the drops with the receiver medium being in the range of 0.5/R less than Di less than 1/R and a final dot size D after spreading on the surface being in the range of 2xc2xd/R less than D less than 2.0/R; and the receiver medium having a surface for receiving the drops, a region of the medium proximate the surface having an influence upon drop spreading and the region having a porosity in the range of 0.2 to 0.8 and sufficient to provide a media drop spread factor Sm wherein Sm=D/Di with 2xc2xd less than Sm less than 2xc3x972xc2xd, the receiver medium or package thereof including indicia associated therewith related to media drop spread factor Sm.
In accordance with a third aspect of the invention, there is provided a single pass inkjet printer comprising a printhead having a plurality of nozzles that are selectively operable for depositing drops of liquid ink or other liquid used in forming of an image in a single pass upon a surface of a receiver medium with a printing resolution R, a dot size Di of the dots resulting from impact of the drops with the receiver medium being in the range of 0.5/R less than Di less than 1/R and a final dot size D after spreading on the surface being in the range of 2xc2xd/R less than D less than 2.0/R; and an input for receiving a signal representing indicia associated with the medium related to media drop spread factor Sm wherein Sm=D/Di, wherein D is the final dot size on the medium after printing by the inkjet printer and Di is the dot size of a drop deposited on the receiver medium and resulting from impact with the receiver medium.
In accordance with a fourth aspect of the invention, there is provided an inkjet printing method recording an image in a single pass print mode, the method comprising providing a printhead having a plurality of nozzles and selectively operating the printhead to deposit drops of liquid ink or other liquid used in forming of an image in a single pass print mode upon a surface of a receiver medium with a printing resolution R, a dot size Di of the dots resulting from impact of the drops with the medium being in the range 0.5/R less than Di less than 1/R and a final dot size D after spreading on the surface being at least 2xc2xd/R less than D less than 2.0/R; and wherein the receiver medium has the surface for receiving the drops, a region of the receiver medium proximate the surface having an influence upon drop spreading and the region having a porosity in the range of 0.2 to 0.8 and sufficient to provide a media drop spread factor Sm wherein Sm=D/Di with 2xc2xd less than Sm less than 2xc3x972xc2xd.
In accordance with a fifth aspect of the invention, there is provided a method of inkjet printing comprising providing a printhead having a plurality of nozzles and selectively operating the printhead to deposit drops of liquid ink or other liquid used in forming of an image in a single pass upon a surface of a receiver medium with a printing resolution R, a dot size Di of the dots resulting from impact of the drops with the receiver medium being in the range of 0.5/R less than Di less than 1/R and a final dot size D after spreading on the surface being in the range 2xc2xd/R less than D less than 2.0/R; and providing a signal representing indicia associated with the medium related to media drop spread factor Sm wherein Sm=D/Di, wherein D is the final dot size on the medium after printing by the inkjet printer and Di is the dot size of a drop deposited on the receiver medium and resulting from impact with the medium; and in response to the signal controlling a drop size or sizes of drops emitted from the nozzles.